En la Región Loreto

There was a main effect for side F(1,38)= 7.64, p = .009, ηp²= .17.

Collapsed over both age groups, the differences between the hemispheres was greater for right targets than left targets

(left target M= -5.30, S.D. = 23 <right target M= 8.54, S.D.= 26.98, p = .012) Right targets elicited earlier negative N1 amplitudes over the contralateral LH M= 208ms, S.D. = 26.17 than the RH M =217ms, S.D. = 27.411.

Left targets elicited earlier negative N1 amplitudes over the RH M= 210ms, S.D. = 25.54 than the LH M= 215ms, S.D. = .27.32

This main effect was qualified by the interaction between age and side F(1, 38)= 5.09, p = .03 ηp²= .12 for the N1 latency.

Further analyses revealed that, within age groups, only young adults revealed differences between target sides.

Within age groups

Young adults showed greater latency differences in right over left targets. L M= -4.58, S.D. = 26.37, R M= 20.58, S.D.= 26.31, t(19)= -3.19, p= .005 , with earlier latencies over the contralateral hemispheres.

Based on the raw latency data, N1 amplitudes peaked earlier for right targets in the LH M= 193ms, S.D. = 25.44 over the RH M= 217ms, S.D. = 25.97.

Left targets showed earlier latencies in the contralateral RH M = 203ms, S.D. = 28.22 over the LH M= 208ms, S.D. = 30.18 (see Table 6).

Between age groups

Independent samples t-tests revealed that between age groups, right targets showed significant differences in latency between the hemispheres, with a greater difference between the LH and the RH in

Young M= 20.59, S.D.= 26.31 over older adults M= -3.5, S.D.= 22.38, t(38)= 3.12, p = .003.

The raw latency data revealed that right targets in young adults elicited earlier N1 amplitudes in the contralateral LH.

LH M= 197ms, S.D. = 25.44 over the RH M= 217ms, S.D. = 25.97.

For older adults, this pattern was reversed with earlier amplitudes in the RH M = 216ms, S.D. = 29.08 over the LH M= 220ms, S.D. = 21.76 although the difference between the LH and the RH in the older adults was small

P2

Table 9: P2 Summary of significant results with aging effects in bold

P2 Amplitude

Main effect: Target side F(1,38)= 11.44, p = .002, ηp²= .23

Interaction: Target side x Age F(1,38)= 28.12, p< .001, ηp²= .43 Interaction: Age x Load x Target

Side

F(2, 76)= 6.02, p =.004, ηp²= .14 Latency

Main effect: Target side F(1,38)= 11.43, p = .002, ηp² = .23 8) P2 Amplitude

Effects of Side:

There was a significant main effect for side F(1,38)= 11.44, p = .002, ηp²= .23, with greater difference in the lateralization of the P2 amplitudes between the hemispheres for right targets M= .55, S.D.= 1.6 than left M= -.42, S.D.= 1.49. The activity was stronger in the opposite direction to the previous components, showing enhanced amplitudes in ipsilateral rather than contralateral

hemispheres.

The raw data revealed that for right targets, P2 amplitudes were surprisingly more enhanced over the RH M= .39, S.D. = 1.36 with smaller in activity in the LH M= -.16, S.D. = 1.80. For left targets, P2 amplitudes were also more enhanced over the ipsilateral LH M= .033, S.D.= 1.26 and smaller in the RH M= -.10, S.D. = 2.04.

There was also an interaction between age and side F(1,38)= 28.12, p< .001, ηp²= .43 .

Right Targets:

Independent samples t-test revealed that between age groups, right targets showed significant differences in lateralization, with a larger difference for the older adults M= 1.5, S.D.= 1.17 than young M= -.41, S.D.= 1.46.,

t(38)= -4.63, p< .001.

Moreover, the two groups revealed dominant activation in opposing

hemispheres: based on the raw data (see Table 6), right targets in older adults showed larger peak activity over the ipsilateral RH M= .35, S.D. = 1.23 and a smaller, negative amplitude over the LH M= -1.17, S.D. = 1.38.

Young adults in contrast showed enhanced peak P2 amplitudes over the contralateral LH M= .85, S.D. = 1.59 vs. the RH M= .43, S.D. = 1.50. This could suggest an age related lateralization shift.

Left Targets:

Again, for left targets, older adults showed a greater difference between the hemispheres than the young adults.

Older M= -.98, S.D. = 1.45 > Young M= .13, S.D.= 1.35 t(38)= 2.52, p = .016. Based on the raw P2 amplitude data (see Table 6), older adults showed again more positive P2 amplitudes over the ipsilateral LH M= .06, S.D. = 1.2

and a negative amplitude over the contralateral RH M = -.93, S.D. = 1.68. Young adults in contrast showed the expected enhanced P2 amplitudes over the contralateral RH M= .73, S.D. = 2.03 and a smaller amplitude over the

LH M = .60, S.D. = 1.27.

Within age groups

Within age groups only older adults showed significant differences in asymmetry between left and right targets (left target M= -.98 S.D. = 1.45 vs

right target M= 1.52), pointing towards a greater difference for right targets between the hemispheres t(19) = -5.66, p < .001.

The raw data revealed that older adults showed more positive P2 amplitudes in the ipsilateral hemispheres, while contralateral hemispheres showed negative peaks.

Left Targets LH M= .06, S.D. = 1.2 vs. RH M=-.93, S.D. = 1.68,

Right Targets LH M= -1.17, S.D. = 1.38 vs. RH M= .35, S.D. = 1.23 (see Table 6).

Effects of Load:

Finally, there was a three way interaction between age, load and side F(2, 76)= 6.02, p =.004 ηp²= .14.

Left Targets :

A follow up 2 Age x 3 Load ANOVA for the left targets revealed no significant effects or interactions.

Right Targets:

A follow up 2 Age x 3 Load ANOVA for the right targets revealed no significant main effect but a significant interaction between Load and Age

F(2, 76)= 4.19, p=.019 ηp²= .10.

In order to investigate the direction of the interaction a series of t-tests were calculated. Between age groups, there were significant differences in all three load conditions (see Figure 26).

No Load

NL Young M= -.74, S.D.= 2.28 , Old M= 1.772, S.D.= 1.42, t(38)= 4.09, p< .001 There was a greater difference between the hemispheres in older adults

compared to the young adults. Young adults showed enhanced peaks over the LH M= 1.48, S.D. = 2.01 than the RH M= .74, S.D. = 1.94.

Older adults showed enhanced peak amplitudes over the RH M= 0.31, S.D. 1.40 and a negative amplitude over the LH M= -1.4, S.D. = 1.58 (see Table 4).

Low Load

The same pattern was repeated for Low load young M= -.52, S.D.= 1.25, Older M= 1.5, S.D.= 1.11, t(38)= -5.15, p< .001, with the raw data showing the following amplitudes for young adults:

LH M= 0.86, S.D. = 1.58 > RH M= 0.34, S.D. = 1.41. Older adults:

LH M= -1.11, S.D.= 1.33. < RH M= .39, S.D.= 1.20 (see Table 4).

High Load

In the High load condition, older adults also showed significantly greater differences between the hemispheres than the young adults.

Young M= .01, S.D.= 1.31, Old M= 1.33, t(38) = -3.26, p= .002.

Older adults showed a lateralization to the RH M=.36, S.D.= 1.09 > LH M= -.98, S.D. = 1.22, while young adults showed minimal differences in lateralization LH M= 0.21, S.D. = 1.17 < RH M= 0.22, S.D.= 1.14 (see Table 4).

Within age groups

Within age groups, paired samples t-tests revealed a significant difference for young adults between low load and high load right targets

Low M= -.52, S.D.= 1.36 vs High M= .01, S.D.= 1.31 t(19)= -2.30, p = .03. No other pairs were significant. The raw peak data revealed that in the low attentional load, RH lateralization was more pronounced and a difference between the hemispheres nearly absent in the High load condition.

Low Load: Young adults LH M= 0.86, S.D. = 1.58 > RH M= 0.34, S.D. = 1.41. High Load: LH M= 0.21, S.D. = 1.17 < RH M= 0.22, S.D. = 1.14 (see Table 4 ).

9) P2 Latency